Arnold-Chiari Malformation Type III With Meningoencephalocele

Arnold-Chiari malformation type III (CM III) is an extremely rare anomaly with poor prognosis. An encephalocele with brain anomalies as seen in CM II, and herniation of posterior fossa contents like the cerebellum are found in CM III.

(A) T1-weighted axial view and (B) T2-weighted sagittal view of brain magnetic resonance imaging at birth show a large sac with cerebellar herniation through the occipital area.(A) Photograph and (B) T1-weighted sagittal view of brain magnetic resonance imaging at 22 months show meningocele at the craniocervical junction with hydrocephalus after removal of the hydrocele.